1. Technical Field
The present invention relates to touchless toggle switches. In particular, it relates to sensor systems capable of measuring background and foreground light with a single sensor, detecting the presence of an object even when the background energy creates a saturation condition in the detector, and discriminating between motion intended to toggle a switch and other forms of motion.
2. Background Art
A variety of applications can benefit from the replacement of mechanical switches or control mechanisms with non-mechanical switches. For example, public facilities used by individuals not responsible for the equipment they use are susceptible to misuse and damage which can often be avoided through the replacement of mechanical switching devices with non-mechanical devices less prone to damage or misuse. Likewise, individuals in occupations which require high levels of cleanliness, such as health care or laboratory personnel, also benefit from the ability to activate devices without coming into physical contact with them.
Several known techniques have been used in the past to provide switch activation which is accomplished without moving a mechanical switch lever or touching. In situations where mechanical activation of switches is inappropriate or difficult, such as in billboards or street lights, automatic systems are known which use photocells to measure ambient light to determine when the lamps in the billboards or street lights are to be activated. These devices use ambient light only and do not provide any method of selectively activating the lights.
Another technique has been the use of a light emitter which projects light through an aperture in a housing assembly. Included in the same housing assembly are a plurality of photocells which are activated when a fingertip covers the aperture. Of course, this technique typically requires that the user actually touch the housing assembly to activate the switch. Further, there is no provision for measuring ambient light.
Other switching devices have been based on the use of a continuously activated emitter/photocell combination which is activated when the beam is broken or reflected back. This type of device is typically used in alarm systems; automatic controls such as those used for water valve controls, sometimes used in conjunction with timing delay or actuation methods or circuits.
A common drawback to many of the aforementioned systems is that the measurement of background or ambient light required dedicated components and the measurement of reflected or continuous direct light required a separate set of components. Due to the requirement for a large number of components, placement of switches in small areas is difficult. Further, prior detection systems have been based on the detection of a reflected light beam or break in a continuous light beam, and not on the measurement of differences in ambient light versus reflected light.
Another significant drawback to prior art solutions is that typically only the presence of an object is detected. The disadvantage to this type of detection is that the presence of an object does not always indicate that the switch is desired to be toggled. For example, a touchless switch in a medical or dental light used to illuminate patients can be advantageous in that the attending medical personnel do not have to risk contamination when toggling the lamp on or off. However, since the lights are generally in close proximity with the physician and patient, the physician can inadvertently toggle the switch. The prior art has not provided a method of preventing accidental toggling of touchless switches in this type of application.
Another serious drawback of prior art systems is their inability to detect objects in conditions of ambient saturation. Ambient saturation is caused when background energy levels are so high that even if an object is within the normal detectable distance from the sensor, it is undetectable because no difference can be measured whether an object is or is not near the sensor.
The prior art has failed to provide a single system which can detect the presence of an object by measuring the difference between ambient light and reflected light. Further, the prior art has failed to provide an effective method of preventing accidental toggling of touchless light switches when the lights are used in close proximity to the user or in conditions of either ambient saturation or non saturation.